you need to make sure the food is not too big for the anemone so you may need to cut it. IF the anemone is new to the tank do not try feeding it for a week or so. I know people who dont feed them , they can survive on what they get from the lighting, your lighting needs to have enough watt per gal
... I feed mine once or twice a month a small piece of shrimp. My clowns feed it small pieces of mysis once in a while..
The biggest thing is water quality, you need a mature tank with great water quality.
My True tank raised percs took to the BTA in a few days.. I have read that even tank raised clowns will host, it is in there geans so having tanked raised fish is not always the reason for the clown not hosting. Some clowns just won;t host with certain anemones.